See ftp://ftp.lcp.nrl.navy.mil/pub/nuttcp/README about xinetd setup.
Just put the nuttcp4 xinetd script into place (and enable it).
Only need the hosts.allow rule if running as a service.

Server listens on the -P "nuttcp" control port, defaulting to 5000.
Clients control the -p "nuttcp-data" port , which defaults to 5001.

Server side opens the nuttcp port.
The data Receiver side (which may be either server or client) opens
 nuttcp-data port.

Server always runs in BG (by the methods I list, at least).
Run server manually like:
    nuttcp -1   # to answer one request then die
or
    nuttcp -S

Run client like
    nuttcp -t server.host.name
    nuttcp -r server.host.name   ( May need -F also if behind a firewall)

Checking packet loss
    nuttcp -u -i -Ri50m server.host.name